Selective Antagonist Research Articles

Pharmacokinetics of Trazodone in Hispaniolan Parrots (Amazona ventralis).

The objective of this study was to establish the pharmacokinetics of a single oral dose of trazodone in the Hispaniolan Amazon parrot (Amazona ventralis). Trazodone is a selective serotonin antagonist and reuptake inhibitor used commonly in both human and veterinary medicine as an antidepressant behavioral modification medicine. A single oral dose of compounded trazodone hydrochloride solution (20 mg/mL) at 50 mg/kg was administered to a total of 7 healthy adult Hispaniolan Amazon parrots. The 7 healthy adult parrots ranged in age from 10 to 15 years and weighed 228 to 323g. Blood was collected at baseline (2 weeks before study) and at 1, 2, 4, 6, 10, and 14 hours post-drug administration. Plasma concentrations of both trazodone and its active metabolite m-chlorophenylpiperazine (mCPP) were measured via liquid chromatography tandem mass spectrometry. Noncompartmental pharmacokinetic analysis was completed. The half-life (t1/2) ± SD of trazodone for the Hispaniolan parrots was 1.89 ± 0.49 hours, and the t1/2 ± SD of mCPP metabolite was 1.9 ± 0.55 hours. Maximum serum drug concentrations, or Cmax (ng/mL), were 738.3 ± 285.3 for trazodone. Times to achieve Cmax (hours) for trazadone and the mCPP metabolite were 1 hour and 2 hours postdosing, respectively. While this study did not establish the behavioral effects of trazodone, no adverse side effects were observed throughout the 48-hour period following drug administration and blood collection. Our results indicate that the oral administration of a 50-mg/kg single dose of trazodone to Hispaniolan parrots may be considered a safe dose. Plasma concentrations are comparable to previously published values in humans, dogs, horses, and pigeons (Columba livia domestica) for up to 14 hours following dosing. This study indicates that further studies are needed to establish the pharmacodynamics and the efficacy of trazodone in the medical management of behavioral problems in psittacine species.

Validation and Application of Thresholds to Define Meaningful Change in Vasomotor Symptoms Frequency: Analysis of Pooled SKYLIGHT1 and 2 Data.

Vasomotor symptoms (VMS), the characteristic symptoms of menopausal transition, are often the primary reason women seek treatment. Current treatment options for VMS include fezolinetant, a nonhormonal, selective neurokinin3 receptor antagonist. This study aimed to define a clinically meaningful threshold for reduction of moderate-to-severe VMS in postmenopausal women treated with fezolinetant and then apply it in a responder analysis of the pooled trial data. This analysis pooled data from two identical phase3, double-blind, placebo-controlled studies that randomized women with moderate-to-severe VMS to once-daily fezolinetant 30mg, 45mg, or placebo (SKYLIGHT1 and 2). The frequency of VMS was collected daily using an electronic diary. Patients completed the Patient Global Impression of Change in VMS (PGI-C VMS) instrument, which assessed changes in hot flushes/night sweats at weeks4 and 12 compared with baseline using a seven-point Likert scale. VMS frequency data were anchored to PGI-C VMS data; the anchor level for meaningful within-patient change in PGI-C VMS was "moderately better." In the pooled population (N = 1022), the mean (standard deviation) estimated thresholds for a meaningful within-patient change in moderate-to-severe VMS frequency were - 5.73 (3.47) at week4 and - 6.20 (5.18) at week12. Applying the thresholds for meaningful within-patient change to responder analyses ("missing as non-responder" imputation method) indicated a favorable clinical benefit: greater proportions of responders were observed in the fezolinetant 30-mg and 45-mg groups compared with placebo at week4 (odds ratio range 2.48-2.91; P < 0.001) and week12 (odds ratio range 1.908-2.68; P < 0.001). PGI-C VMS is sensitive to change and correlates with VMS frequency: a reduction of approximately six VMS episodes per day from baseline to week12 was meaningful at the individual patient level. Fezolinetant provides a meaningful clinical benefit for women with moderate-to-severe VMS associated with menopause and represents an important nonhormonal treatment option. NCT04003155 and NCT04003142.

Evolution of sex-biased genes in Drosophila species with neo-sex chromosomes: Potential contribution to reducing the sexual conflict.

An advantage of sex chromosomes may be the potential to reduce sexual conflict because they provide a basis for selection to operate separately on females and males. However, evaluating the relationship between sex chromosomes and sexual conflict is challenging owing to the difficulty in measuring sexual conflict and substantial divergence between species with and without sex chromosomes. We therefore examined sex-biased gene expression as a proxy for sexual conflict in three sets of Drosophila species with and without young sex chromosomes, the so-called neo-sex chromosomes. In all sets, we detected more sex-biased genes in the species with neo-sex chromosomes than in the species without neo-sex chromosomes in larvae, pupae, and adult somatic tissues but not in gonads. In particular, many unbiased genes became either female- or male-biased after linkage to the neo-sex chromosomes in larvae, despite the low sexual dimorphism. For example, genes involved in metabolism, a key determinant for the rate of development in many animals, were enriched in the genes that acquired sex-biased expression on the neo-sex chromosomes at the larval stage. These genes may be targets of sexually antagonistic selection (i.e., large size and rapid development are selected for in females but selected against in males). These results indicate that acquiring neo-sex chromosomes may have contributed to a reduction in sexual conflict, particularly at the larval stage, in Drosophila..

Serotonin receptor-mediated vasorelaxation occurs primarily through 5-HT4 activation in bovine lateral saphenous vein.

To better understand mechanisms of serotonin- (5-HT) mediated vasorelaxation, isolated lateral saphenous veins from cattle were assessed for vasoactivity using myography in response to increasing concentrations of 5-HT or selective 5-HT receptor agonists. Vessels were pre-contracted with 1 × 10-4 M phenylephrine and exposed to increasing concentrations of 5-HT or 5-HT receptor agonists that were selective for 5-HT1B, 5-HT2B, 5-HT4, and 5-HT7. Vasoactive response data were normalized as a percentage of the maximum contractile response induced by the phenylephrine pre-contraction. At 1 × 10-7 M 5-HT, a relaxation was observed with an 88.7% decrease (p < 0.01) from the phenylephrine maximum. At 1 × 10-4 M 5-HT, a contraction was observed with a 165% increase (p < 0.01) from the phenylephrine maximum. Increasing concentrations of agonists selective for 5-HT2B, 5-HT4, or 5-HT7 resulted in a 27%, 92%, or 44% (p < 0.01) decrease from the phenylephrine maximum, respectively. Of these 5-HT receptor agonists, the selective 5-HT4 receptor agonist resulted in the greatest potency (-log EC50) value (6.30) compared with 5-HT2B and 5-HT7 receptor agonists (4.21 and 4.66, respectively). To confirm the involvement of 5-HT4 in 5-HT-mediated vasorelaxation, blood vessels were exposed to either DMSO (solvent control) or a selective 5-HT4 antagonist (1 × 10-5 M) for 5-min prior to the phenylephrine pre-contraction and 5-HT additions. Antagonism of the 5-HT4 receptor attenuated the vasorelaxation caused by 5-HT. Approximately 94% of the vasorelaxation occurring in response to 5-HT could be accounted for through 5-HT4, providing strong evidence that 5-HT-mediated vasorelaxation occurs through 5-HT4 activation in bovine peripheral vasculature.

A Bicyclic Analog of the Linear Peptide Arodyn Is a Potent and Selective Kappa Opioid Receptor Antagonist.

Kappa opioid receptor (KOR) antagonists have potential therapeutic applications in the treatment of stress-induced relapse to substance abuse and mood disorders. The dynorphin A analog arodyn (Ac[Phe1,2,3,Arg4,D-Ala8]dynorphin A-(1-11)-NH2) exhibits potent and selective kappa opioid receptor antagonism. Multiple cyclizations in longer peptides, such as dynorphin and its analogs, can extend the conformational constraint to additional regions of the peptide beyond what is typically constrained by a single cyclization. Here, we report the design, synthesis, and pharmacological evaluation of a bicyclic arodyn analog with two constraints in the opioid peptide sequence. The peptide, designed based on structure-activity relationships of monocyclic arodyn analogs, was synthesized by solid-phase peptide synthesis and cyclized by sequential ring-closing metathesis (RCM) in the C- and N-terminal sequences. Molecular modeling studies suggest similar interactions of key aromatic and basic residues in the bicyclic peptide with KOR as found in the cryoEM structure of KOR-bound dynorphin, despite substantial differences in the backbone conformations of the two peptides. The bicyclic peptide's affinities at KOR and mu opioid receptors (MOR) were determined in radioligand binding assays, and its KOR antagonism was determined in the [35S]GTPγS assay in KOR-expressing cells. The bicyclic analog retains KOR affinity and selectivity (Ki = 26 nM, 97-fold selectivity over MOR) similar to arodyn and exhibits potent KOR antagonism in the dynorphin-stimulated [35S]GTPγS assay. This bicyclic peptide represents a promising advance in preparing cyclic opioid peptide ligands and opens avenues for the rational design of additional bicyclic opioid peptide analogs.

Generic viability qPCR for monitoring shelf life of microbial biological control agents coated on seeds based on the nucleic acid intercalating dyes EMA and PMAxx

Biological control of seedborne pathogens and soilborne seedling pathogens through antagonists applied on seeds is an alternative to chemical seed treatments. Information on the viability of inocula on treated seeds is essential for any development and use of beneficial fungi or bacteria on seeds. Generic fungal and bacterial qPCR assays were combined with the nucleic acid intercalating dyes ethidium monoazide (EMA) and propidium monoazide (PMAxx) for the quantification of viable cells of fungi and bacteria on seeds. The applied protocols for generic fungal viability qPCR (v-qPCR) in combination with EMA and PMAxx and for generic bacterial v-qPCR in combination with PMAxx allowed the viability quantification of fungal and bacterial isolates representing a broad range of species with the exception of fungal species with highly melanized conidia. A first application of v-qPCR to coated seeds of onion and spinach indicated a differential plant species effect on survival of a coated fungus and a yeast with a generally better survival on seeds of spinach compared to seeds of onions and a similar good survival of the bacterium L. enzymogenes 3.1T8 on both seed types. The v-qPCR protocols can be applied in screening assays aiming at the selection of new antagonists with higher survival potentials and the development of new seed processing technologies compatible with coated antagonists.

Activation of Piezo1 or TRPV2 channels inhibits human ureteral contractions via NO release from the mucosa.

We aimed to investigate the expression and motor modulatory roles of several mechano-sensitive channels (MSCs) in human ureter. Human proximal ureters were obtained from eighty patients subjected to nephrectomy. Expression of MSCs at mRNA, protein and functional levels were examined. Contractions of longitudinal ureter strips were recorded in organ bath. A fluorescent probe Diaminofluoresceins was used to measure nitric oxide (NO). RT-PCR analyses revealed predominant expression of Piezo1 and TRPV2 mRNA in intact ureter and mucosa. Immunofluorescence assays indicate proteins of MSCs (Piezo1/Piezo2, TRPV2 and TRPV4) were mainly distributed in the urothelium. Ca2+ imaging confirmed functional expression of TRPV2, TRPV4 and Piezo1 in cultured urothelial cells. Specific agonists of Piezo1 (Yoda1, 3-300μM) and TRPV2 (cannabidiol, 3-300μM) attenuated the frequency of ureteral contractions in a dose-dependent manner while the TRPV4 agonist GSK1016790A (100nM-1μM) exerted no effect. The inhibitory effects of Piezo1 and TRPV2 agonists were significantly blocked by the selective antagonists (Dooku 1 for Piezo1, Tranilast for TRPV2), removal of the mucosa, and pretreatment with NO synthase inhibitor L-NAME (10μM). Yoda1 (30μM) and cannabidiol (50μM) increased production of NO in cultured urothelial cells. Our results suggest that activation of Piezo1 or TRPV2 evokes NO production and release from mucosa that may mediate mechanical stimulus-induced reduction of ureter contractions. Our findings support the idea that targeting Piezo1 and TRPV2 channels may be a promising pharmacological strategy for ureter stone passage or colic pain relief.

Real-Life Experience on the Effect of SGLT2 Inhibitors vs. Finerenone vs. Combination on Albuminuria in Chronic Kidney Disease.

There have been several recent advances in the care of patients with chronic kidney disease (CKD), including the use of sodium glucose cotransporter 2 (SGLT2) inhibitors and selective mineralocorticoid receptor antagonists (MRAs). There are very few data reporting the outcomes of these treatments in real-world experience. The aim of this retrospective study is to report the effects of SGLT2 inhibitors, finerenone, and their combination in CKD patients in our community-based setting. Ninety-eight patients with CKD with an estimated glomerular filtration rate (eGFR) between 25 and 90 mL/min per 1.73 m2 and a urine albumin-to-creatinine ratio (UACR) ≥ 30 mg/g were included. Patients were divided into three groups: two monotherapy groups of SGLT2 inhibitors or finerenone and a third combination group of therapy with SGLT2 inhibitors for the first 4 months and SGLT2 inhibitors and finerenone subsequently. The primary outcomes were the timing and percentage of patients achieving a >50% reduction in UACR from baseline. Group 1 comprised 52 patients on SGLT2i, group 2 had 22 patients on finerenone, and group 3 had 24 patients on combination therapy. The baseline median UACR and mean eGFR were 513 mg/g and 47.9 mL/min per 1.73 m2 in group 1, 548.0 mg/g and 50.5 mL/min per 1.73 m2 in group 2, and 800 mg/g and 60 mL/min per 1.73 m2 in group 3. At baseline, 71 (72.4%) patients were on the angiotensin-converting enzyme inhibitor (ACEi) or the angiotensin receptor blocker (ARB), and 78 (79.5%) patients had type 2 diabetes. After 8 months of follow-up, a >50% decrease in albuminuria was achieved in 96% of patients in group 3, compared to 50% in group 1 and 59% in group 2 (p-values were <0.01 and <0.01, respectively). There was a statistically but not clinically significant change in mean potassium levels in group 2 (+0.4 mmol/L) compared to either group 1 (0.0 mmol/L with p-value: <0.01) or group 3 (-0.01 mmol/L with p-value: <0.01). However, there was no difference in potassium levels when comparing groups 1 and 3. At the end of the follow-up, the average difference in eGFR was -3.4 (8.8), -5.3(10.1), and -7.8 (11.2) mL/min per 1.73 m2 in groups 1, 2, and 3, respectively, without a statistically significant difference between groups. In this real-world experience in our community setting, the combination of SGLT2 inhibitors and finerenone in our adult patients with CKD was associated with a very significant and clinically relevant reduction in UACR, without an increased risk of hyperkalemia. Combination therapy of SGLT2 inhibitor and finerenone regarding background use of ACEi/ARB is feasible and should be encouraged for further albuminuria reductions in CKD patients.

5-hydroxytryptamine 2C/1A receptors modulate the biphasic dose response of the head twitch response and locomotor activity induced by DOM in mice.

The phenylalkylamine hallucinogen (-)-2,5-dimethoxy-4-methylamphetamine (DOM) exhibits an inverted U-shaped dose-response curve for both head twitch response (HTR) and locomotor activity in mice. Accumulated studies suggest that HTR and locomotor hyperactivity induced by DOM are mainly caused by the activation of serotonin 5-hydroxytryptamine 2A receptor (5-HT2A receptor). However, the mechanisms underlying the biphasic dose response of HTR and locomotor activity induced by DOM, particularly at high doses, remain unclear. The primary objective of this study is to investigate the modulation of 5-HT2A/2C/1A receptors in HTR and locomotor activity, while also exploring the potential receptor mechanisms underlying the biphasic dose response of DOM. In this study, we employed pharmacological methods to identify the specific 5-HT receptor subtypes responsible for mediating the biphasic dose-response effects of DOM on HTR and locomotor activity in C57BL/6J mice. The 5-HT2A receptor selective antagonist (R)-[2,3-di(methoxy)phenyl]-[1-[2-(4-fluorophenyl)ethyl]piperidin-4-yl]methanol (M100907) (500µg/kg, i.p.) fully blocked the HTR at every dose of DOM (0.615-10mg/kg, i.p.) in C57BL/6J mice. M100907 (50µg/kg, i.p.) decreased the locomotor hyperactivity induced by a low dose of DOM (0.625, 1.25mg/kg, i.p.), but had no effect on the locomotor hypoactivity induced by a high dose of DOM (10mg/kg) in C57BL/6J mice. The 5-HT2C antagonist 6-chloro-5-methyl-1-[(2-[2-methylpyrid-3yloxy]pyrid-5yl)carbamoyl]indoline (SB242084) (0.3, 1mg/kg, i.p.) reduced the HTR induced by a dose of 2.5mg/kg DOM, but did not affect the response to other doses. SB242084 (1mg/kg, i.p.) significantly increased the locomotor activity induced by DOM (0.615-10mg/kg, i.p.) in mice. The 5-HT1A antagonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]N-(2-pyridinyl) cyclohexane carboxamide maleate (WAY100635) (1mg/kg, i.p.) increased both HTR and locomotor activity induced by DOM in mice. The 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) (1mg/kg, i.p.) significantly reduced both the HTR and locomotor activity induced by DOM in mice. Additionally, pretreatment with the Gαi/o inhibitor PTX (0.25µg/mouse, i.c.v.) enhanced the HTR induced by DOM and attenuated the effect of DOM on locomotor activity in mice. Receptor subtypes 5-HT2C and 5-HT1A are implicated in the inverted U-shaped dose-response curves of HTR and locomotor activity induced by DOM in mice. The biphasic dose-response function of HTR and locomotor activity induced by DOM has different mechanisms in mice.

Involvement of dopamine D3 receptor in impulsive choice decision-making in male rats

Impulsive decision-making has been linked to impulse control disorders and substance use disorders. However, the neural mechanisms underlying impulsive choice are not fully understood. While previous PET imaging and autoradiography studies have shown involvement of dopamine and D2/3 receptors in impulsive behavior, the roles of distinct D1, D2, and D3 receptors in impulsive decision-making remain unclear. In this study, we used a food reward delay-discounting task (DDT) to identify low- and high-impulsive rats, in which low-impulsive rats exhibited preference for large delayed reward over small immediate rewards, while high-impulsive rats showed the opposite preference. We then examined D1, D2, and D3 receptor gene expression using RNAscope in situ hybridization assays. We found that high-impulsive male rats exhibited lower levels of D2 and D3, and particularly D3, receptor expression in the nucleus accumbens (NAc), with no significant changes in the insular, prelimbic, and infralimbic cortices. Based on these findings, we further explored the role of the D3 receptor in impulsive decision-making. Systemic administration of a selective D3 receptor agonist (FOB02-04) significantly reduced impulsive choices in high-impulsive rats but had no effects in low-impulsive rats. Conversely, a selective D3 receptor antagonist (VK4-116) produced increased both impulsive and omission choices in both groups of rats. These findings suggest that impulsive decision-making is associated with a reduction in D3 receptor expression in the NAc. Selective D3 receptor agonists, but not antagonists, may hold therapeutic potentials for mitigating impulsivity in high-impulsive subjects.

5-HT6 receptor neutral antagonists protect astrocytes: A lesson from 2-phenylpyrrole derivatives

The serotonin type 6 receptor (5-HT6R) displays a strong constitutive activity, suggesting it participates largely in the physiological and pathological processes controlled by the receptor. The active states of 5-HT6R engage particular signal transduction pathways that lead to different biological responses. In this study, we present the development of 5-HT6R neutral antagonists at Gs signaling built upon the 2-phenylpyrrole scaffold. Using molecular dynamics simulations, we outline the relationship between the exposure of the basic center of the molecules and their ability to target the agonist-activated state of the receptor. Our study identifies compound 30 as a potent and selective neutral antagonist at 5-HT6R-operated Gs signaling. Furthermore, we demonstrate the cytoprotective effects of 30 and structurally diverse 5-HT6R neutral antagonists at Gs signaling in C8-D1A cells and human astrocytes exposed to rotenone. This effect is not observed for 5-HT6R agonists or inverse agonists. In light of these findings, we propose compound 30 as a valuable molecular probe to study the biological effects associated with the agonist-activated state of 5-HT6R and provide insight into the glioprotective properties of 5-HT6R neutral antagonists at Gs signaling.

Selective anti-CXCR2 receptor blockade by AZD5069 inhibits CXCL8-mediated pro-tumorigenic activity in human thyroid cancer cells in vitro.

Thyroid cancer is the most common endocrine malignancy. Current therapies are successful, however some patients progress to therapeutically refractive disease. The immunotherapeutic potential of the CXCL8-chemokine/CXCR2-chemokine-receptor system is currently being explored in numerous human cancers. This study aimed to evaluate if the targeting of CXCR2 by its selective antagonist, AZD5069, could modulate CXCL8-mediated pro-tumorigenic effects in thyroid-cancer (TC) cells in vitro. Normal human primary thyroid cells (NHT) and TC cell lines TPC-1 (RET/PTC), BCPAP, 8505C and 8305C (BRAFV600e) were treated with AZD5069 (100pM-10µM) over a time-course. Viability and proliferation were assessed by WST-1 and crystal violet assays. CXCL8 and CXCR2 mRNA were evaluated by RT-PCR. CXCL8-protein concentrations were measured in cell culture supernatants by ELISA. CXCR2 on cell surface was evaluated by flow-cytometry. Cell-migration was assessed by trans-well-migration chamber-system. AZD5069 exerted negligible effects on cell proliferation or viability. AZD5069 significantly reduced CXCR2, (but not CXCL8) mRNAs in all cell types. CXCR2 was reduced on the membrane of some TC cell lines. A significant reduction of the CXCL8 secretion was found in TPC-1 cells (basal-secretion) and NHT (TNFα-induced secretion). AZD5069 significantly reduced basal and CXCL8-induced migration in NHT and different TC cells. Our findings confirm the involvement of the CXCL8/CXCR2-axis in promoting pro-tumorigenic effects in TC cells, further demonstrating its immunotherapeutic significance in human cancer.

(046) THE ROLE OF ADENOSINE IN THE RELAXANT MECHANISM OF RAT DISTAL VAGINA

Abstract Introduction Adenosine (ADO) is a purinergic neuromodulator that in the male exerts a positive effect on penile erection by controlling smooth muscle (SM) relaxation. However, its role in the relaxant/contractile pathways in the vagina is yet to be investigated. Objective The aim of this study was to characterize the effect of ADO stimulation on SM activity in distal vagina, evaluating its possible effect on the regulation of nitric oxide (NO) pathway using a validated animal model of female Sprague-Dawley rats. Methods The immunolocalization of ADORA2A and ADORA2B in distal vagina tissues was detected by immunohistological staining. In vitro contractility studies on noradrenaline (NA)-precontracted vaginal strips from intact Sprague-Dawley rats were performed; rat smooth muscle cells (rvSMCs) from distal vagina of intact animals were stimulated with ADO for cyclic adenosine monophosphate (cAMP) quantification. mRNA (messenger ribonucleic acid) isolated from vaginal tissue was analyzed by semi-quantitative Reverse Transcriptase-Polymerase Chain Reaction. Results All ADORAs mRNA were expressed in the vaginal tissue, with a significant prevalence of ADORA2B; furthermore, ADORA2A and ADORA2B immunolocalization highlighted that both receptors are highly expressed in the epithelium, in blood capillaries of the vascular bed and in the smooth muscle bundles of vagina wall. In vitro ADO stimulation induced a dose-dependent relaxation (IC50=31.9±2.38 μM), which was significantly reduced by the administration of NO-synthase inhibitor L-NAME; similar effects were observed after the mechanical ablation of endothelium and in vitro administration of the soluble guanylate cyclase inhibitor ODQ, highlighting the pivotal contribution of NO signaling to the ADO relaxant activity. In vitro stimulation with increasing doses of the selective ADO receptor ADORA2A agonist CGS2-1680 induced a dose-dependent relaxation (IC50=132.6±3.47 nM); a similar but less potent relaxant effect was observed with ADORA2B selective agonist BAY60-6583. The relaxing effect induced by ADO on NA-precontracted vaginal strips was completely counteracted by the stimulation with the re-spectively selective ADORA2A and ADORA2B antagonists SHC-442416 and PSB603; a similar effect was induced by ADORA1 selective antagonist SLV320, but not by ADORA3 selective antagonists VUF5574. The mRNA relative expression of enzymes regulating the ADO turnover [adenosine deami-nase (ADA), 5′-nucleotidase (5NTD), AMP deaminase type 1 and type 2 (AMPD1, AMPD2) and adenosine kinase (ADK)] showed a higher expression of genes regulating the de novo ADO/cAMP syn-thesis (ADK, 5NTD), compared to those acting on ADO degradation (ADA, AMPD1, AMPD2). Finally, stimulation of rvSMCs with increasing doses of ADO induced a significant production of intracellular cAMP after 3 minutes (1 and 10 μM). Conclusions These data show that ADO acts as an important relaxant modulator of the vagina through the activation of its receptors, specifically ADORA2A, and the consequent cAMP-dependent adenylate cyclase re-sponse. However, in vitro studies show that ADO also acts trough the NO-dependent pathway. These results therefore demonstrate for the first time a new relaxant pathway in distal vagina, ADO signaling, that results deeply intertwined with the well-known NO pathway. This finding unravels new biological mechanisms underlying vagina physiology that need to be further studied in future research. Disclosure No.

Molecular Interactions of Selective Agonists and Antagonists with the Retinoic Acid Receptor γ.

All-trans retinoic acid (ATRA), the major active metabolite of all-trans retinol (vitamin A), is a key hormonal signaling molecule. In the adult organism, ATRA has a widespread influence on processes that are crucial to the growth and differentiation of cells and, in turn, the acquisition of mature cell functions. Therefore, there is considerable potential in the use of retinoids to treat diseases. ATRA binds to the retinoic acid receptors (RAR) which, as activated by ATRA, selectively regulate gene expression. There are three main RAR isoforms, RARα, RARβ, and RARγ. They each have a distinct role, for example, RARα and RARγ regulate myeloid progenitor cell differentiation and hematopoietic stem cell maintenance, respectively. Hence, targeting an isoform is crucial to developing retinoid-based therapeutics. In principle, this is exemplified when ATRA is used to treat acute promyelocytic leukemia (PML) and target RARα within PML-RARα oncogenic fusion protein. ATRA with arsenic trioxide has provided a cure for the once highly fatal leukemia. Recent in vitro and in vivo studies of RARγ have revealed the potential use of agonists and antagonists to treat diseases as diverse as cancer, heterotopic ossification, psoriasis, and acne. During the final drug development there may be a need to design newer compounds with added modifications to improve solubility, pharmacokinetics, or potency. At the same time, it is important to retain isotype specificity and activity. Examination of the molecular interactions between RARγ agonists and the ligand binding domain of RARγ has revealed aspects to ligand binding that are crucial to RARγ selectivity and compound activity and key to designing newer compounds.

A Second Drug Binding Site in P2X3.

Purinergic P2X3 receptors form trimeric cation-gated channels, which are activated by extracellular ATP. P2X3 plays a crucial role in chronic cough and affects over 10% of the population. Despite considerable efforts to develop drugs targeting P2X3, the highly conserved structure within the P2X receptor family presents obstacles for achieving selectivity. Camlipixant, a potent and selective P2X3 antagonist, is currently in phase III clinical trials. However, the mechanisms underlying receptor desensitization, ion permeation, principles governing antagonism, and the structure of P2X3 when bound to camlipixant remain elusive. In this study, we established a stable cell line expressing homotrimeric P2X3 and utilized a peptide scaffold to purify the complex and determine its structure using cryo-electron microscopy (cryo-EM). P2X3 binds to camlipixant at a previously unidentified drug-binding site and functions as an allosteric inhibitor. Structure-activity studies combined with modeling and simulations have shed light on the mechanisms underlying the selective targeting and inhibition of P2X3 by camlipixant, distinguishing it from other members of the P2X receptor family.

GLUT1 mediates bronchial epithelial E-cadherin disruption in TDI-induced steroid-insensitive asthma

Objective Down-regulation of bronchial epithelial E-cadherin is an important of feature of severe asthma, including steroid-insensitive asthma. Yet, the mechanisms involved in E-cadherin disruption are not fully understood. This study was aimed to investigate the role of glucose transporter 1 (GLUT1) in dysregulation of E-cadherin in toluene diisocyanate (TDI)-induced steroid-insensitive asthma. Methods A murine model of steroid-insensitive asthma was established by TDI sensitization and aerosol inhalation. Selective GLUT1 antagonists WZB117 and BAY876 were given to BALB/c mice after airway challenge. In vitro, primary human bronchial epithelial cells (HBECs) cultured in an airway-liquid interface (ALI) were exposed to TDI. Results TDI exposure markedly up-regulated GLUT1 in murine lungs and HBECs. Pharmacological inhibition of GLUT1 with BAY876 decreased airway hyperresponsiveness, neutrophil and eosinophil accumulation, as well as type 2 inflammation in vivo. Besides, the TDI-induced down-regulated expression of full-length E-cadherin was also partly recovered, accompanied by inhibited secretion of soluble E-cadherin (sE-cadherin). WZB117 also exhibited mild therapeutic effects, though not significant. In vitro, treatment with GLUT1 inhibitor relieved the TDI-induced disruption of E-cadherin in HBECs. Conclusions Taken together, our data demonstrated that GLUT1 modulates bronchial epithelial E-cadherin dysfunction production in TDI-induced steroid-insensitive asthma.

Navacaprant, a novel and selective kappa opioid receptor antagonist, has no agonist properties implicated in opioid-related abuse

Kappa opioid receptors (KORs) are implicated in the pathophysiology of various psychiatric and neurological disorders creating interest in targeting the KOR system for therapeutic purposes. Accordingly, navacaprant (NMRA-140) is a potent, selective KOR antagonist being evaluated as a treatment for major depressive disorder. In the present report, we have extended the pharmacological characterization of navacaprant by further demonstrating its selective KOR antagonist properties and confirming its lack of agonist activity at KORs and related targets involved in opioid-related abuse. Using CHO–K1 cells expressing human KOR, mu (MOR), or delta (DOR) opioid receptors, navacaprant demonstrated selective antagonist properties at KOR (IC50 = 0.029 μM) versus MOR (IC50 = 3.3 μM) and DOR (IC50 > 10 μM) in vitro. In vivo, navacaprant (10–30 mg/kg, i.p.) dose-dependently abolished KOR-agonist induced analgesia in the mouse tail-flick assay. Additionally, navacaprant (10, 30 mg/kg, p.o.) significantly reduced KOR agonist–stimulated prolactin release in mice and rats, confirming KOR antagonism in vivo. Navacaprant showed no agonist activity at any opioid receptor subtype (EC50 > 10 μM) in vitro and exhibited no analgesic effect in the tail-flick assays at doses ≤100 mg/kg, p.o. thereby confirming a lack of opioid receptor agonist activity in vivo. Importantly, navacaprant did not alter extracellular dopamine concentrations in the nucleus accumbens shell of freely-moving rats following doses ≤100 mg/kg, p.o., whereas morphine (10, 20 mg/kg, i.p.) significantly increased dopamine levels. These results demonstrate that navacaprant is a KOR-selective antagonist with no pharmacological properties implicated in opioid-related abuse.

The pharmacological blockade of P2X4 receptor as a viable approach to manage visceral pain in a rat model of colitis

Nowadays, the pharmacological management of visceral hypersensitivity associated with colitis is ineffective. In this context, targeting purinergic P2X4 receptor (P2X4R), which can modulate visceral pain transmission, could represent a promising therapeutic strategy. Herein, we tested the pain-relieving effect of two novel and selective P2X4R antagonists (NC-2600 and NP-1815-PX) in a murine model of DNBS-induced colitis and investigated the mechanisms underlying their effect. Tested drugs and dexamethasone (DEX) were administered orally, two days after colitis induction. Treatment with tested drugs and DEX improved tissue inflammatory parameters (body weight, spleen weight, macroscopic damage, TNF and IL-1β levels) in DNBS-rats. In addition, NC-2600 and NP-1815-PX attenuated visceral pain better than DEX and prevented the reduction of occludin expression. In in vitro studies, treatment of CaCo2 cells with supernatant from THP-1 cells, previously treated with LPS plus ATP, reduced the expression of tight junctions protein. By contrast, CaCo2 cells treated with supernatant from THP-1 cells, previously incubated with tested drugs, counteracted the reduction of tight junctions due to the inhibition of P2X4R/NLRP3/IL-1β axis. In conclusion, these results suggest that the direct and selective inhibition of P2X4R represents a viable approach for the management of visceral pain associated with colitis via NLRP3/IL-1β axis inhibition.

Effects of psilocin and psilocybin on human 5-HT4 serotonin receptors in atrial preparations of transgenic mice and humans

Several fungi belonging to the genus Psilocybe, also called “magic mushrooms”, contain the hallucinogenic drugs psilocybin and psilocin. They are chemically related to serotonin (5-HT). In addition to being abused as drugs, they are now also being discussed or used as a treatment option for depression. Here, we hypothesized that psilocybin and psilocin may act also on cardiac serotonin receptors and studied them in vitro in atrial preparations of our transgenic mouse model with cardiac myocytes-specific overexpression of the human 5-HT4 receptor (5-HT4-TG) as well as in human atrial preparations. Both psilocybin and psilocin enhanced the force of contraction in isolated left atrial preparations from 5-HT4-TG, increased the beating rate in isolated spontaneously beating right atrial preparations from 5-HT4-TG and augmented the force of contraction in the human atrial preparations. The inotropic and chronotropic effects of psilocybin and psilocin at 10 µM were smaller than that of 1 µM 5-HT on the left and right atria from 5-HT4-TG, respectively. Psilocybin and psilocin were inactive in WT. In the human atrial preparations, inhibition of the phosphodiesterase III by cilostamide was necessary to unmask the positive inotropic effects of psilocybin or psilocin. The effects of 10 µM psilocybin and psilocin were abrogated by 10 µM tropisetron or by 1 µM GR125487, a more selective 5-HT4 receptor antagonist. In summary, we demonstrated that psilocin and psilocybin act as agonists on cardiac 5-HT4 receptors.

Transient Receptor Potential Ankyrin 1 Channel Alters Transforming Growth Factor Beta 1/Smad Signaling in Rat Vocal Fold Fibroblasts.

Vocal fold scar remains a therapeutic challenge. Vocal fold fibroblasts (VFFs) secrete extracellular matrix (ECM), and transforming growth factor-beta 1 (TGF-β1)-mediated fibroblast to myofibroblast differentiation is central to the development of fibrosis. The transient receptor potential (TRP) channel superfamily is a group of nonselective cation channels, and activation of TRP ankyrin 1 (TRPA1) channel has been shown to have antifibrotic effects through TGF-β1/Smad signaling in various organs. This study aimed to elucidate expression of TRPA1 and the impact of TRPA1 activation on TGF-β1/Smad signaling in VFFs. Vocal folds were dissected from 10-week-old, male Sprague-Dawley rats and primary VFFs were established. TRPA1 was examined in VFFs and lamina propria via immunostaining. VFFs were treated with allyl isothiocyanate (AITC, TRP channel agonist, 10-5 M) ± TGF-β1 (10 ng/ml) ± A-967079 (selective TRPA1 channel antagonist, 5.0 × 10-7 M) for 4 or 24 h. Trpa1, Smad3, Smad7, Col1a1, Acta2, and Has1 mRNA expression were quantified via qPCR. TRPA1 was expressed in cultured VFFs and the lamina propria. TGF-β1 administration significantly increased Trpa1 compared to control. AITC alone did not alter Smad3, Smad7, Acta2, or ECM related genes. However, the combination of AITC and TGF-β1 significantly increased Smad3 and decreased Smad7 and Acta2 compared to TGF-β1 alone; A-967079 significantly reduced this response. VFFs expressed TRPA1, and the activation of TRPA1 regulated TGF-β1/Smad signaling in VFFs. These findings provide preliminary insights into potential anti-fibrotic mechanisms of TRPA1 activation through TGF-β1/Smad signaling in VFFs. NA Laryngoscope, 134:4593-4598, 2024.